The ETag was the pixel hash of the original image, so a CoverArtQuality or
EnableWebPEncoding change altered the resized bytes without changing the ETag —
revalidating clients got a spurious 304 and kept the old encoding. Resized responses
now carry a representation ETag (hash + size + square + encode settings) used for the
ETag header and If-None-Match, while the immutable decision stays on the pixel hash
(URLs remain pixel-identity per the spec, so hash-suffixed clients keep zero-request
caching). Full-size originals fall back to the pixel hash as before.
DiscCoverArtID returns a dc- id for any track with DiscNumber>0, so serveDisc ran
the full DiscArtPriority chain even for single-disc albums, where a stray disc*/
embedded image could shadow higher-priority album art. Gate disc resolution on the
album having more than one disc, matching the legacy reader; single-disc tracks
serve album art directly.
serveMediaFile delegated an absent/ineligible track straight to AlbumCoverArtID,
skipping the disc-specific lookup that MediaFile.CoverArtID (and the deleted legacy
reader) use. On multi-disc albums with per-disc images that served the album cover
instead of the configured disc artwork. Delegate through DiscCoverArtID.
